Keywords:
Arabidopsis thaliana, flavonol biosynthesis, flavonol glycoside, flavonol glycosyltransferases, plant growth, polar auxin transportAbstract:
- Polar auxin transport (PAT) plays key roles in the regulation of plant growth and development.
Flavonoids have been implicated in the inhibition of PAT. However, the active flavonoid derivative(
s) involved in this process in vivo has not yet been identified. Here, we provide evidence that
a specific flavonol bis-glycoside is correlated with shorter plant stature and reduced PAT.
- Specific flavonoid-biosynthetic or flavonoid-glycosylating steps were genetically blocked in
Arabidopsis thaliana. The differential flavonol patterns established were analyzed by highperformance
liquid chromatography (HPLC) and related to altered plant stature. PAT was
monitored in stem segments using a radioactive [3H]-indole-3-acetic acid tracer.
- The flavonoid 3-O-glucosyltransferase mutant ugt78d2 exhibited a dwarf stature in addition
to its altered flavonol glycoside pattern. This was accompanied by reduced PAT in
ugt78d2 shoots. The ugt78d2-dependent growth defects were flavonoid dependent, as they
were rescued by genetic blocking of flavonoid biosynthesis. Phenotypic and metabolic analyses
of a series of mutants defective at various steps of flavonoid formation narrowed down
the potentially active moiety to kaempferol 3-O-rhamnoside-7-O-rhamnoside. Moreover,
the level of this compound was negatively correlated with basipetal auxin transport.
- These results indicate that kaempferol 3-O-rhamnoside-7-O-rhamnoside acts as an endogenous
PAT inhibitor in Arabidopsis shoots.DOI: